Power transmission



Patented Aug. 15, 1950 POWER TRANSIHISSION Ferris T. Iiarrington,Detroit, and Ralph L. Tweedale,

Birmingham, Mich., assignors to Vickers Incorporated, Detroit, Mich., acorporation of Michigan Application May 17, 1947, Serial No. 748,752

This invention relates to power transmissions, particularly to those ofthe type comprising two or more fluid 'pressure energy translatingdevices, one of which may function as a pump and another as a fluidmotor.

The invention is more particularly concerned with ,a power transmissionsystem of the type disclosed in the patent to Herman, No. 2,274,603. Thetransmission therein disclosed is comprised of a pressure fluid source,a reversible fluid motor for operating a load device, and a controlpanel containing the necessary valving for producing a rapid advance,coarse feed, fine feed, rapid reverse, and stop operation of the loa Thevalving contained in the panel is comprised of a control valve and flowcontrol mechanism, the latter of which consists of a'coarse feedthrottle, a fine feed throttle, and a pressure compensating valve. Thecompensating valve is of g the well known type which is responsive tothe pressure drop across the throttle for maintaining a constantlyregulated flow of fluid through the throttle. The compensating valveassumes numerous regulating positions in response to the pressure dropacross the throttle for regulating the flow through the latter. However,when fluid flow ceases through the compensating valve, it is biased to anon-regulating, fully open position. The control valve is shiftable toone position for connecting the coarse feed throttle and compensatingvalve to the exhaust end of the motor for producing a coarse feedmovement of the motor. The con- .trol valve is also shiftable to anotherposition for connecting the throttles in series and the compensatingvalve to-the exhaust end of the motor for producing a fine feed movementof the motor. When the control valve is shifted to the motor stopposition, fluid flow through the flow regulating valve mechanism .isinterrupted.

In the past, some difficulty has been experienced when the load deviceis started into a feeding position from rest. This difliculty lies inthe inability of the compensating valve to immediately assume anormalregulating position. During the time interval that this requires, fluidis exhausted from the motor at a greater than normal rate causing theslide to jump ahead at the beginning of a feed movement. This isparticularly objectionable in'machine tools where, for some reason, itmay be necessary to stop the slide during the middle of a cut and thenif the feed-- ing movement be resumed, the slide jumps ahead momentarilycausing breaking of the cutting tool.

Claims. (CI. 60-52) I 2 provide an improved control panel whichovercomes this dimculty.

. It is a further object of this invention to provide in a panel of thistype a back pressure valve for inducing a flow of pressure fluid throughthe flow regulating valve mechanism when the motor is stopped. In thismanner, if the motor is restarted in a feedmovement after interruptionthereof, the compensating valve will already be in a flow regulatingposition and motor jump will be prevented.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings ,wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Figure 1 is a circuit diagram and cross section of a control panelembodying a preferred form of the present invention and showing thepassageways in the same plane for purposes of illustration.

Figure 2 is a view corresponding to that of Figure 1, but showing thecontrol valve in the panel shifted to another position.

Figure 3 is a view corresponding to that of Figure 1 but showing thecontrol valve therein shifted to still another position.

Figure 4 is a view corresponding to that of Figure 1, but showing thecontrol valve therein shifted to still another position. v

Referringnow to Figure 1, there is shown a pump I0 which may be drivenby an electric motor l2 and which is connected to a tank M by means of asuction conduit Iii. A pressure fluid delivery conduit I8 is connectedto the pump ll) and to a pressure inlet port 20 of a control panel 2 2.The panel 22 is also provided with a tank port 24 which is connected tothe tank I4 by means of a conduit 26 and with motor ports 28 and 30which are connected to opposite ends of a fluid motor 32 by means ofconduits 34 and. 36. The motor 32 is of the reciprocating type having apiston 38 connected to which is a piston rod 40 which extends throughthe motor. The motor 32 may be connected inthe conventional manner to areciprocating work table of a machine tool (not shown) for the purposeof driving the same.

A control valve 42 is shiftably mounted in a bore 44 of the panel 22.The control valve 42 is provided with a centrally located land 46, lands48 and 50 on either side of land 46, andextreme end lands 52 and 54. Thelands control ports spaced along the bore 44 including a pressure port56,

It therefore an object of. invention to 55 motor ports I8 and located onopposite sides 3 of port 88, extreme opposite end tank ports 82 an 84,and throttle ports 88 and 88. The external pressure, tank, and motorports 20, 24, 28, and 30 are respectively separately connected to theircorresponding valve bore ports by means of conduits I0, I2, I4, and I8;A branch conduit I8 of the motor conduit I8 is connected to an inletchamber I9 and an outlet chamber 80 of a pressure compensating valve 82,to a bore 84 within which is mounted a coarse feed throttle 88, to thethrottle port 88, and to a bore 88 within which is mounted a fine feedthrottle 90. The flne feed throttle bore 88' is connected to the valvebore throttle port 84 by means of a conduit 92. The tank port 82 isconnected to the tank conduit 12 by means of a conduit 94.

Mounted within the conduit 94 is a back pressure valve 98. A drainconduit 98 connects the lower end of thevalve bore 44 to the tankconduit I2 while a drain conduit I connects the upper end of the bore 44to the tank port 24. The compensating valve 82 is comprised of a pistonI02 connected to which is a stem I04 having an upper land I08 and atapered lower land forming a valve I08 which controls fluid flow betweenthe inlet chamber I8 and the outlet chamber 80. A spring 0 ofpredetermined resistance located in an upper chamber II2 of thecompensating valve 82 in abutting relationship with the piston I02biases the valve I08 to the fully open position. The compensating valve82 is adapted to be responsive port 30 must flow to the tank I4 by meansof conduits I8 and I8, compensating valve 82, coarse feed throttle 88,valve bore ports 88, 88, and 84,

to the pressure ahead of the throttles 88 and 90 by means of a conduitII4 which connects the outlet chamber 80 to a pressure chamber II8 belowthe piston I02. The compensating valve 82 is adapted to be responsive tothe pressure beyond the throttles 88 and 90 by means of a branch conduitII8 of the drain conduit I00 which is connected to the upper chamber H2.The valve 42 is adapted to be shifted by means of a ball-ended rod I20connected to the lower end of the valve 42, the former of which isconnected to a rotatable shaft I22. The shaft I22 is adapted to berotated during the movement of the member being reciprocated at variousstages of the cycle of the movement in the conventional manner.Incorporated in the pump delivery conduit I8 is relief valve I24 ofsuitable construction which adapted to exhaust to the tank I4, excessivepressure fluid by means of a conduit I28.

Referring nowto Figure 1, in operation, with the valve 42 shifted to the,position shown in Figure 1, a rapid advance movement of the motor 32will take place. Pressure fluid entering the pressure port 20 isconducted to the external motor port 28 by means of conduit 10, valvebore ports 58 and 58, and conduit I4, and to the head end of the motor32 by means of conduit 34.

Fluid is free to discharge from the rod end of the motor 32 to the tankI4 by; means of conduit 38, motor port 30, conduit I8, valve bore ports80, 88, 88, and 84, conduit 12, tank port 24, and conduit 28.

Referring now to Figure 2, the valve 42 is shifted during the rapidadvance movement of the motor to the position shown in Figur 2, a coarsefeed movement of the motor will take place. Pressure fluid from the pumpI0 is delivered to the head end of the motor 32 in the same manner asdescribed in the rapid advance movement. However, discharging fluid fromthe rod end of the motor 32 must flow to the tank through thecompensating valve 82 and coarse feed throttle 88. The land 48 blocksthe valve conduit I2, tank port 24, and conduit 28. Al though theconduit I8 is also open to fine feed throttle 90, the fluid will takethe course of at least resistance and ow to the tank I4 rather thanthrough the flne feed throttle 80. The com pensating valve 82 willfunction in-the well known manner to maintain the pressure drop acrossthe throttle 88 constant and thereby maintain a uniform flow through thethrottle. The resistance of the spring IIO determines the pressure dropacross the throttle. Any increase of pressure ahead of the throttle 88in conduit I8 is immediately present in chamber I I8 to shift the pistonI02 upwardly and thus the valve I08 towards the closed position torestrict the flow of fluid from the inlet chamber I9 to the outletchamber 80. A decrease of pressure in conduit I8 ahead of the throttle88 results in an immediate decrease of pressure in the lower chamber H8and the spring IIO will shift the piston I02 downwardly resulting in thevalve I08 moving towards the open position to permit more flow fluidfrom the inlet chamber 19 to the outlet chamber 80. The valve I08 willassume numerous regulating positions between the fully open and fullyclosed positions for maintaining the pressure drop across the throttleuniformly constant.

It should be noted that if fluid flow is interrupted to the compensatingvalve and throttle that the spring I I0 will bias valve I08 to the fullyopen p sition or a non-regulating position.

If the valve 42 is shifted slightly downward from the position shown inFigure 2, a' fine feed movement of the motor 32 will take place. Fluidis continued to be directed to the head end of the motor, the same as inthe rapid advance and coarse feed cycles of the motor. Fluid dischargingfrom the motor must also flow through the compensating valve 82 and thecoarse feed throttle 88 as in the coarse feed cycle of the motor.However, the land 50 will now block the conduit I8 from the port 88 andfluid must flow from the coarse feed throttle 88 through the flne feedthrottle 90, as shown by dotted arrows, and thence to the tank I4 bymeans of conduit 92, valve ports 88 and 84, conduit |2, external tankport 24, and conduit 28. Due to the fact that throttle 90 and throttle88 are now connected in series, and, because throttle 90 produces agreater restriction than throttle 88, the latter throttle will not beeffective. The compensating valve 82 will maintain a constant pressuredrop across the throttle 90 in the same manner as the throttle 88 in thecoarse feed movement. Consequently, the flow across the throttle 90 willbe uniformly regulated at the rate desired.

Referring now to Figure 3, if thevalve 42 is shifted to the positionshown, the motor 32, will be stopped. The pressure port 20 is directlyconnected to the tank port 24 by means of conduit 10, valve ports '88,58, and 82, conduit 94, back pressure valve 98, and conduit 12. However,the back pressure valve 88 is adapted to have suflicient resistance todivert a portion of the pump flow through the compensating valve 82 andthe throttles 88 and 90. The resistance created by the back pressurevalve 98 will direct a portion of pump flow through valve ports 58 and88, conduits I8' and I8, compensating valve 82 and throttle 88, valveport 88, throttle 90, conduit 92, valve ports 88 and 84, and conduit 12to bore motor port and fluid entering the motor 1; the tank port 24. Theresistance of the back pressure'valve 6 will be set to divert a portionof this pump flow through the flow regulating valve mechanism withoutcausing excessive heating within the system.

- Referring now to Figure 4, if the valve 42 is shifted to the positionshown in Figure 4, a rapid return movement of the motor will take place.Fluid from the pump Ill entering pressure port 20 is conducted to motorport 30 by means of conduit 10, valve ports 56 and 60, and conduit 18,and thence to the rod end of the motor 32 by means of conduit 36. Fluidfrom the head end of the motor 32 is discharged to the tank II by meansof conduit 34, motor port 28, conduit I4. valve ports 58 and 62, conduit94, back pressure valve 96, conduit 12, tank port 24, and conduit 28.

It should be noted that the valve I is prevented from moving to thefully open position by this procedure and will be maintained in a normalregulating position while the motor is stopped. Consequently, if duringa coarse feed or fine feed movement of the motor, the motor is stoppedand then the feed movement is resumed, the compensating valve 82 will bein a normal regulating position to maintain the flow across either orboth throttles uniformly constant. If the back pressure valve iiii wasnot incorporated in the panel 22, the valve I08 would biased to a fullyopen position, or a non-reguable to immediately assume a regulatingposition. During this time lapse, a flow of fluid from the inlet chamber19 to the outlet chamber Ill would result in excess of which is thenormally regulated amount. This slight but excessive amount of fluidabove the normal regulated amount causes the motor to jump and is thecause of ruining cutting tools.

Thus, by incorporating the back pressure valve in the panel in themanner described, the compensating valve 82 is maintained in a normalregulating position when the motor is stopped, and in particular, whilestopped during a feed movement and is already in a position to maintaina regulated flow of fluid through the throttle when the motor isrestarted in the feed movement.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows: I

1. A unitary control panel for use in av hydraulic power transmissionhaving a fluid pump and reversible fluid motor comprising in combinationa valve block having external connection ports, a control valveconnected to said ports and shiftable to a plurality of positions forcontrolling the motor including motor advance, feed, reverse, and stoppositions, flow control mechanism for producing a feed movement of themotor including a compensating valve of the type which opens fullywhenever the fluid flow through the compensating valve is interrupted,and means for ind cing a flow of presthe control valve is shifted to thestop position thereby operating the compensating valve to a throttlingposition ready to immediately control the feed movement of the motorwhen the control valve is shifted. from the stop to the feed position.

2. A unitary control panel for use in a hydraulic power transmissionhaving a fluid pump and reversible fluid motor comprising in com-'bination a valve block having external connec- .tion ports, a controlvalve connected to said ports and shiftable to a, plurality of positionsfor controlling the motor including motor advance, feed, reverse, and sop positions, flow control mechanism for producing a feed movement ofthe motor including a compensating valve of the type which opens fullywhenever the fluid flow through the compensating valve is interrupted,and a back pressure valve for inducing a flow of pressure fluid throughthe compensating valve when the control valve is shifted to the stopposition thereby operating the compensating valve to a throttlingposition ready to immediately control the feed movement of the motorwhen the control valve is shifted from the stop to the feed position.

3. A unitary control panel for use in a hydraulic power transmissionhaving a fluid pump and reversible fluid motor comprising in combinationa, valve block having external connection ports, flow control mechanismfor producing two different feed rates including a coarse feed throttleand a fine throttle through which fluid is adapted to flow at acontrolled rate and an automatic pressure compensating valve responsiveto the pressure drop across the throttles for maintaining the flow ratethrough the throttles uniformly constant, said compensating valve being01 the type which opens fully when ever the fluid flow through thecompensating valve is interrupted, a control valve connected to saidports and to the flow control' mechanism shiftable to a plurality ofpositions for controlling the motor operation including motor advance,coarse feed, fine feed, reverse, and stop operations thereof, and meansfor inducing a flow of pressure fluid through the compensating valvewhen the control valve is shifted to the stop position thereby operatingthe compensatingvalve to a throttling position ready to immediatelycontrol the movement of the motor when the control valve is shifted fromthe stop position to either of the feed positions.

4. A unitary control panel for use in a hydraulic power transmissionhaving a fluid pump and reversible fluid motor comprising in combinationa valve block having external connection ports, flow control mechanismfor producing two different feed rates including a coarse feed throttleand a fine throttle through which fluid is adapted to flow at acontrolled rate and an automatic pressure compensating valveresponsive'to the pressure drop across the throttles for maintaining theflow rate through the throttles uniformly constant, said compensatingvalve being of the type which opens fully whenever the fluid flowthrough the compensating valve is interrupted, a control valve connectedto said ports and to the flow control mechanism shiftable to a pluralityof positions for controlling the motor operation including motoradvance, coarse feed, fine feed, reverse, and stop operations thereof,and a back pressure valve for inducing a flow of pressure fluid throughthe .sure fluid through the co pensating valve when u compensating valvewhen the control valve is shiited tothe stop position thereby. operatingthe compensating valve to a throttling position ready to immediatelycontrol the movement oi. the motor when the control valve is shiftedfrom the stop position to either of the feed positions.

5 In a. hydraulic power transmission the combination of a fluid source,a fluid pump, a reversible fluid motor, flow control mechanism forregulating the speed of the motor comprising a coarse feed throttle anda fine teed throttle through which fluid is adapted to flow at aregulated rate and an automatic pressure compensating valve responsiveto the pressure drop across the throttles for maintaining the regulatedrate, said compensating valve being of the type which opens fullywhenever the flow through the compensating valve is interrupted, a backpressure valve and a control valve shittable to a ilrst and a secondposition for alternately connecting op- =posite ends of the motor to thesource and the pump and by-passing the flow control mechanism forcausing rapid advance and rapid reverse movements of the motor, to athird position for connecting one end of the motor to the pump and theopposite end 01' the motor to the compensating valve, to the'coarse feedthrottle and to the source for producing a, coarse feed movement of themotor to a fourth position'for connecting the pump to one end of themotor 8 and the opposite end to the throttles in series and thecompensating valve for producing a fine teed movement 01' the motor andto a fifth position for connecting the ump to the back 5 pressure valve,to the compensating valve and to the source for stopping the motor andinducing a flow of pressure fluid through the compensating valve whilethe motor is stopped thereby operating the compensating valve to thethrottling position while the motor is stopped and ready to immediatelycontrol the movement of the motor when the control valve is shifted fromthe stop position tov either the third or fourth positions.

FERRIS T. HARRINGTON. RALPH L. TWEEDALE.

REFERENCES CITED The following references are of record in th file ofthis patent:

UNITED STATES PATENTS

